As an apparatus for storing electric energy, a battery can be significantly applied in many fields. In an application field of fixed energy storage, an apparatus such as a data center device, an optical communications device, or a base station has a relatively high requirement on a battery, and a battery state of charge (SOC) needs to be in an almost fully charged state. The battery inevitably ages during long term use. Therefore, a user pays more attention to battery aging. Specifically, battery aging may be monitored by using a battery state of health (SOH), so as to understand current battery performance.
In some existing application fields, a battery internal resistance is correlated to a battery capacity, but an increase in the battery internal resistance does not necessarily cause a loss in the battery capacity. Comparatively, in most application fields, a battery retention capacity is usually used as a parameter index to measure the battery SOH, and can accurately represent battery capacity information.
Currently, a battery retention capacity parameter is obtained mostly in a checking charge/discharge manner. This manner can be used only in an out-of-service state. As a result, the apparatus such as the data center device, the optical communications device, or the base station cannot normally supply power for a load when the battery is discharged or recharged after discharge, and great impact is exerted on a service. Therefore, the battery state of health needs to be detected in an in-service state. However, such a requirement has not been met currently in the prior art.